In recent years, numerous proposals have been made for use of the clean energy hydrogen as a source of energy.
To produce hydrogen, steam reformation of a hydrocarbon fuel has been the general practice. In recent years, it has been considered to obtain hydrogen from water by the splitting of water, in particular the splitting of water using solar energy. When splitting water to obtain hydrogen, the obtained product sometimes becomes a mixture of hydrogen, oxygen, and water. In this case, to obtain hydrogen, it is necessary to separate and remove only the hydrogen from this mixture.
Regarding the separation of hydrogen from such a mixture of hydrogen, oxygen, and water, Japanese Unexamined Patent Publication (Kokai) No. 2004-35356 and Japanese Unexamined Patent Publication (Kokai) No. 2004-292284 propose using a hydrogen separating membrane selectively allowing the passage of only hydrogen. Note that, Japanese Unexamined Patent Publication (Kokai) No. 2008-207969 proposes using a hydrogen separating membrane for separation of hydrogen from a mixed gas obtained by steam reformation of a hydrocarbon fuel.